Exercise algebra.equations.linear.balance

Description
Solve a linear equation using only balance rules.

Derivation

4*(x-4) == 5*(2*x+1)
algebra.equations.linear.balance.distribute
4*x-16 == 10*x+5
algebra.equations.linear.balance.var-right-minus, term=4*x
-16 == 6*x+5
algebra.equations.linear.balance.con-left-minus, term=5
-21 == 6*x
algebra.equations.linear.balance.scale-to-one, factor=6
-7/2 == x
algebra.equations.linear.flip
x == -7/2